Revista Brasileira de Ornitologia 14 (3) 197-238 setembro de 2006 The avifauna of the Brazilian state of Roraima: bird distribution and biogeography in the Rio Branco basin Luciano Nicolás Naka1,4,5, Mario Cohn-Haft1, Francisco Mallet-Rodrigues2, Marcos Pérsio Dantas Santos3, and Marcela de Fátima Torres1 1 Instituto Nacional de Pesquisas da Amazônia (INPA), Coleções Zoológicas e Coordenação de Pesquisas em Ecologia, C.P. 478 (69011-970), Manaus, Amazonas, Brazil. 2 Laboratório de Ornitologia, Departamento de Zoologia, Instituto de Biologia, UFRJ (21941-590), Rio de Janeiro, Rio de Janeiro, Brazil. 3 Universidade Federal do Piauí, Departamento de Biologia. (64049-550), Teresina, Piauí, Brazil. 4 Current Address: Museum of Natural Science, 119 Foster Hall, Louisiana State University, Baton Rouge, LA 70803, USA. 5 Corresponding author: Luciano Nicolas Naka, e-mail: [email protected] Recebido em 30 de dezembro de 2005; aceito em 22 de maio de 2006 RESUMO. A Avifauna do Estado de Roraima: distribuição e biogeografi a na bacia do Rio Branco. O Estado de Roraima representa uma impor- tante unidade biogeográfi ca, que inclui toda a bacia do Rio Branco, um dos principais rios Amazônicos. Roraima é uma área de alta diversidade, onde fl orestas de terra fi rme, fl orestas alagadas, campinas, savanas, bosques secos e em galeria, e vegetação associada com os tepuis ocorrem em uma área relativamente pequena para padrões Amazônicos (225.000 km2). Neste trabalho, apresentamos a primeira compilação em quarenta anos, das 741 espécies de aves registradas para o Estado de Roraima, 38 das quais representam as primeiras menções para a região. Os dados foram compilados a partir de informações obtidas durante nossas expedicões de campo (512 espécies), complementadas por informacões obtidas de material de museu e da literatura. Apresentamos uma lista com 15 espécies citadas para Roraima no passado, que não consideramos como registros válidos e achamos que sua presença em Roraima ainda deve ser confi rmada, e uma outra lista com 69 espécies que acreditamos venham ser registradas em Roraima no futuro. Apresentamos também detalhes de alguns dos nossos registros de maior interesse, incluíndo o primeiro espécime para o Brasil de Atalotriccus pilaris, e a segunda localidade para o Brasil de Myrmeciza disjuncta. Uma análise dos padrões de distribuição da avifauna, em relação aos diferentes ambientes, revelou que a heterogeneidade ambiental (diversidade beta) é responsável por 60% da diversidade de Roraima, enquanto que o endemismo regional (diversidade gamma) responde por quase um terço das espécies de aves exclusivas de fl orestas de terra fi rme. Apresentamos também uma análise dos padrões biogeográfi cos das aves em Roraima, em relação aos diferente hábitats. E fi nalmente, discutimos os problemas de conservação desta região que encontra-se ameaçada pela crescente expansão de monoculturas (soja, acácias, arroz) principalmente nas áreas de savanas, fl orestas de galeria, e bosques secos, onde habitam algumas das espécies de aves endêmicas e mais ameaçadas da região. PALAVRAS-CHAVE: Amazônia, Roraima, Rio Branco, avifauna, distribuição, biogeografi a. ABSTRACT. The Brazilian state of Roraima represents a meaningful biogeographical unit, enclosing the entire basin of the Rio Branco, a major river in the Amazon basin. Roraima is also an area of high habitat diversity where terra fi rme forest, seasonally fl ooded forest, white-sand forest, savanna, gallery and dry forest, and the vegetation associated with the tepuis, all occur within a relatively small area (225,000km2) by Amazonian standards. We provide the fi rst comprehensive compilation of the avifauna of the state in forty years. We integrated the results of our own fi eld work, where we recorded 512 bird species, with data gathered from museum specimens and from published sources. We present a list of 741 bird species for the state of Roraima, 38 of which are mentioned for the fi rst time for the state. We also provide a list of 15 species previously cited for Roraima that we consider hypothetical, and predict the presence of another 69 species that we consider likely to be recorded in the state with further fi eld work. We also present details on some of our most interesting records, which include the fi rst Brazilian specimen of Atalotriccus pilaris, and the second locality for Brazil of Myrmeciza disjuncta. We conclude that habitat heterogeneity (beta-diversity) is responsible for 60% of the avian diversity of Roraima, whereas regional endemism (gamma-diversity) accounts for about one third of the bird species occurring exclusively in terra fi rme forests. We analyze the biogeographical patterns of avian distributions within the state, in relation to the different habitats present in Roraima, and discuss some of the main conservation problems in the state of Roraima, driven by the expansion of monocultures such as soybean, acacia, and rice plantations which are putting at risk large expanses of savannas, wetlands, dry and gallery forests. KEY WORDS: Amazonia, Roraima, Rio Branco, avifauna, distribution, biogeography. At the northern edge of Amazonia, the Brazilian state of Ro- Amazonian standards. Avian diversity in Roraima refl ects this raima represents one of the most heterogeneous regions in high habitat heterogeneity, as each major habitat contributes the Neotropics. Distinct habitats, including terra fi rme forest, with unique species. Regional diversity is also increased by seasonally fl ooded forest (várzea and igapó), white-sand for- the fact that different areas within Roraima are, to varying de- est (campina and campinarana), savanna, gallery and dry for- grees, biogeographically distinct; at least three proposed areas est, and various types of montane forests, all occur in an area of endemism extend into the state (Cracraft 1985). roughly the size of the United Kingdom, relatively small by Unlike most political units, the state of Roraima represents 198 Luciano Nicolás Naka, Mario Cohn-Haft, Francisco Mallet-Rodrigues, Marcos Pérsio Dantas Santos, and Marcela de Fátima Torres a meaningful biogeographical unit, enclosing the entire basin and some of its tributaries, the white-sand forest (campina and of the Rio Branco, the most important tributary of the Rio campinarana) in central Roraima, and the terra fi rme forest Negro, which itself is the second largest tributary of the Ama- east of the Rio Branco. We integrated our results with data ob- zon River (Goulding et al. 2003). The Rio Branco basin is tained independently by MPDS, and with data from previous unique in Amazonia because its main river, the Rio Branco, is workers available from published sources and museums (data a white-water river surrounded by black-water rivers, which compiled by FMR). differ in the amount of sediments, type of vegetation, and the In this paper, we provide a brief history of ornithologi- structure of the plant community (Worbes 1997). These dif- cal research in Roraima, present our fi eld records, including ferences between the two should also infl uence the abundance 38 bird species recorded for the fi rst time in Roraima, and and composition of the bird species that inhabit each type of provide the fi rst comprehensive compilation of the avifauna river. Therefore, a study of the avifauna of Roraima not only of the state since Pinto (1966). We also make predictions on sheds light on one of the least-studied areas of Brazilian Ama- the species likely to be recorded in the state with further fi eld zonia (Oren and Albuquerque 1991), but can also improve our work and describe the broad patterns of avian distributions understanding of Amazonian avian biogeography, generating within the Rio Branco basin in relation to the different habi- insights on ecological and geographical patterns. tats, discussing the implications of these patterns in a biogeo- Until the mid-20th century, most of the ornithological mate- graphical perspective and giving special attention to the role rial available for Roraima was that obtained by Johann Nat- of the Rio Branco as a biogeographical barrier. terer in the early 1800s. During the second half of the 20th cen- tury, several ornithologists visited or analyzed bird specimens HISTORY OF ORNITHOLOGICAL STUDIES from the state, but these studies concentrated on a few areas, IN RORAIMA including savannas and forests near Boa Vista, the upper Rio Branco, a handful of tepuis on the Brazilian-Venezuelan bor- The study of the avifauna of Roraima began with the ex- der, and the Maracá Ecological Station (see History of orni- plorations of Natterer almost two centuries ago. Since then, a thological studies in Roraima, below). Entire ecosystems and number of ornithologists have visited the region, mostly dur- biogeographic areas remained virtually unexplored until now. ing the last 50 years, defi ning important periods of high pro- In 2001, three of us (LNN, MCH, and MFT) initiated a ductivity in terms of accumulation of ornithological data, and study of the avifauna of Roraima and made fi ve fi eld trips periods of relative stagnation (Figure 1). to the state. We explored poorly sampled habitats and previ- The fi rst naturalist to visit the Rio Branco basin appears ously neglected biogeographical areas, such as the seasonally to have been Alexandre Rodrigues Ferreira, a Brazilian ex- fl ooded forest (várzea and igapó) along the lower Rio Branco plorer sent by the Portuguese crown in 1786 to investigate Figure 1. Cumulative number of bird species known from Roraima since the fi rst related publication in 1850. Decades represent time of publication of lists of specimens or fi eld records. Arrows indicate the explorers or ornithologists responsible for most of the additions during that decade. The avifauna of the Brazilian state of Roraima: bird distribution and biogeography in the Rio Branco basin 199 the economic potential of the region (Barbosa and Ferreira During the following years, most of the attention given to 1997). Ferreira sailed the Rio Branco and some of its tributar- Roraima came from Venezuela, mostly from explorers inter- ies, collecting plants and animals.